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From: Alexandre Oliva <aoliva@gcc.gnu.org>
To: gcc-cvs@gcc.gnu.org
Subject: [gcc(refs/users/aoliva/heads/testme)] [PR105665] ivopts: check defs
 of names in base for undefs
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https://gcc.gnu.org/g:ab0624ba523cb6118ef65962603bc150de66f6e3

commit ab0624ba523cb6118ef65962603bc150de66f6e3
Author: Alexandre Oliva <oliva@adacore.com>
Date:   Thu May 26 09:15:53 2022 -0300

    [PR105665] ivopts: check defs of names in base for undefs

Diff:
---
 gcc/tree-ssa-loop-ivopts.cc | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/gcc/tree-ssa-loop-ivopts.cc b/gcc/tree-ssa-loop-ivopts.cc
index 2e8cd486cc0..e68968efc5f 100644
--- a/gcc/tree-ssa-loop-ivopts.cc
+++ b/gcc/tree-ssa-loop-ivopts.cc
@@ -3074,10 +3074,18 @@ get_loop_invariant_expr (struct ivopts_data *data, tree inv_expr)
 /* Find the first undefined SSA name in *TP.  */
 
 static tree
-find_ssa_undef (tree *tp, int *walk_subtrees, void *)
+find_ssa_undef (tree *tp, int *walk_subtrees, void *pset_)
 {
+  auto pset = static_cast<hash_set<tree> *> (pset_);
+
   if (TREE_CODE (*tp) == SSA_NAME)
     {
+      /* If we've already visited this SSA_NAME and got to it again,
+	 we know we didn't find it to be undefined, otherwise we'd
+	 have stopped the walk then.  */
+      if (pset && pset->add (*tp))
+	return NULL;
+
       if (ssa_undefined_value_p (*tp, false))
 	return *tp;
 
@@ -3092,8 +3100,10 @@ find_ssa_undef (tree *tp, int *walk_subtrees, void *)
 	{
 	  tree use = USE_FROM_PTR (use_p);
 
-	  if (ssa_undefined_value_p (use, false))
-	    return use;
+	  int wsub = 1;
+	  tree result = find_ssa_undef (&use, &wsub, pset);
+	  if (result)
+	    return result;
 	}
     }
 
@@ -3132,7 +3142,8 @@ add_candidate_1 (struct ivopts_data *data, tree base, tree step, bool important,
   /* If BASE contains undefined SSA names make sure we only record
      the original IV.  */
   bool involves_undefs = false;
-  if (walk_tree (&base, find_ssa_undef, NULL, NULL))
+  hash_set<tree> pset;
+  if (walk_tree (&base, find_ssa_undef, &pset, NULL))
     {
       if (pos != IP_ORIGINAL)
 	return NULL;